dnschneid/crouton

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: 18

crouton is a set of scripts that bundle up into an easy-to-use, Chromium OS-centric chroot generator. Currently Ubuntu and Debian are supported (using debootstrap behind the scenes), but "Chromium OS Debian, Ubuntu, and Probably Other Distros Eventually Chroot Environment" doesn't acronymize as well (crodupodece is admittedly pretty fun to say, though).

"crouton"...an acronym?

It stands for ChRomium Os Universal chrooT envirONment ...or something like that. Do capitals really matter if caps-lock has been (mostly) banished, and the keycaps are all lower-case?

Moving on...

Who's this for?

Anyone who wants to run straight Linux on their Chromium OS device, and doesn't care about physical security. You're also better off having some knowledge of Linux tools and the command line in case things go funny, but it's not strictly necessary.

What's a chroot?

Like virtualization, chroots provide the guest OS with their own, segregated file system to run in, allowing applications to run in a different binary environment from the host OS. Unlike virtualization, you are not booting a second OS; instead, the guest OS is running using the Chromium OS system. The benefit to this is that there is zero speed penalty since everything is run natively, and you aren't wasting RAM to boot two OSes at the same time. The downside is that you must be running the correct chroot for your hardware, the software must be compatible with Chromium OS's kernel, and machine resources are inextricably tied between the host Chromium OS and the guest OS. What this means is that while the chroot cannot directly access files outside of its view, it can access all of your hardware devices, including the entire contents of memory. A root exploit in your guest OS will essentially have unfettered access to the rest of Chromium OS.

Prerequisites

You need a device running Chromium OS that has been switched to developer mode.

For instructions on how to do that, go to this Chromium OS wiki page, click on your device model and follow the steps in the Entering Developer Mode section.

Note that developer mode, in its default configuration, is completely insecure, so don't expect a password in your chroot to keep anyone from your data. crouton does support encrypting chroots, but the encryption is only as strong as the quality of your passphrase. Consider this your warning.

It's also highly recommended that you install the crouton extension, which, when combined with the extension or xiwi targets, provides much improved integration with Chromium OS.

That's it! Surprised?

Usage

crouton is a powerful tool, and there are a lot of features, but basic usage is as simple as possible by design.

If you're just here to use crouton, you can grab the latest release from https://goo.gl/fd3zc. Download it, pop open a shell (Ctrl+Alt+T, type shell and hit enter), and run sh ~/Downloads/crouton to see the help text. See the "examples" section for some usage examples.

If you're modifying crouton, you'll probably want to clone or download the repo and then either run installer/main.sh directly, or use make to build your very own crouton. You can also download the latest release, cd into the Downloads folder, and run sh crouton -x to extract out the juicy scripts contained within, but you'll be missing build-time stuff like the Makefile.

crouton uses the concept of "targets" to decide what to install. While you will have apt-get in your chroot, some targets may need minor hacks to avoid issues when running in the chrooted environment. As such, if you expect to want something that is fulfilled by a target, install that target when you make the chroot and you'll have an easier time. Don't worry if you forget to include a target; you can always update the chroot later and add it. You can see the list of available targets by running sh ~/Downloads/crouton -t help.

Once you've set up your chroot, you can easily enter it using the newly-installed enter-chroot command, or one of the target-specific start* commands. Ta-da! That was easy.

Examples

The easy way (assuming you want an Ubuntu LTS with Xfce)

Download crouton

Open a shell (Ctrl+Alt+T, type shell and hit enter) and run sudo sh ~/Downloads/crouton -t xfce

Wait patiently and answer the prompts like a good person.

Done! You can jump straight to your Xfce session by running sudo enter-chroot startxfce4 or, as a special shortcut, sudo startxfce4

Cycle through Chromium OS and your running graphical chroots using Ctrl+Alt+Shift+Back and Ctrl+Alt+Shift+Forward.

Exit the chroot by logging out of Xfce.

With encryption!

Add the -e parameter when you run crouton to create an encrypted chroot or encrypt a non-encrypted chroot.

You can get some extra protection on your chroot by storing the decryption key separately from the place the chroot is stored. Use the -k parameter to specify a file or directory to store the keys in (such as a USB drive or SD card) when you create the chroot. Beware that if you lose this file, your chroot will not be decryptable. That's kind of the point, of course.

Hey now, Ubuntu 16.04 is pretty old; I'm young and hip

The -r parameter specifies which distro release you want to use.

Run sh ~/Downloads/crouton -r list to list the recognized releases and which distros they belong to.

Wasteful redundancies are wasteful: one clipboard, one browser, one window

If you installed cli-extra, startcli will launch a new VT right into the chroot.

A new version of crouton came out; my chroot is therefore obsolete and sad

Check for updates, download the latest version, and see what's new by running croutonversion -u -d -c from the chroot (run croutonversion -h to see what those parameters actually do).

Exit the chroot and run sudo sh ~/Downloads/crouton -u -n chrootname. It will update all installed targets.

I want to open my desktop in a window or a tab but I don't have the 'xiwi' target/xmethod.

Add 'xiwi' or any other target to an existing chroot with the '-u' option using: sudo sh ~/Downloads/crouton -t xiwi -u -n chrootname

This will also make 'xiwi' the default xmethod.

If you want to keep the 'xorg' xmethod as the default then enter it first using: sudo sh ~/Downloads/crouton -t xorg,xiwi -u -n chrootname

A backup a day keeps the price-gouging data restoration services away

sudo edit-chroot -b chrootname backs up your chroot to a timestamped tarball in the current directory. Chroots are named either via the -n parameter when created or by the release name if -n was not specified.

sudo edit-chroot -r chrootname restores the chroot from the most recent timestamped tarball. You can explicitly specify the tarball with -f

If your machine is new, powerwashed, or held upside-down and shaken, you can use the crouton installer to restore a chroot and relevant scripts: sudo sh ~/Downloads/crouton -f mybackup.tar.gz

Unlike with Chromium OS, the data in your chroot isn't synced to the cloud.

This chroot's name/location/password/existence sucks. How to fix?

Check out the edit-chroot command; it likely does what you need it to do.

If you set a Chromium OS root password, you can change it with sudo chromeos-setdevpasswd

You can change the password inside your chroot with passwd

I want to install the chroot to another location

Use -p to specify the directory in which to install the chroot and scripts. Be sure to quote or escape spaces.

When entering the chroot, either specify the full path of the enter-chroot or start* scripts (i.e. sudo sh /path/to/enter-chroot), or use the -c parameter to explicitly specify the chroots directory.

Issues?

Running another OS in a chroot is a pretty messy technique (although it's hidden behind very pretty scripts), and these scripts are relatively new, so problems are not surprising. Check the issue tracker and file a bug if your issue isn't there. When filing a new bug, include the output of croutonversion run from inside the chroot or, if you cannot mount your chroot, include the output of cat /etc/lsb-release from Crosh.

I want to be a Contributor!

That's great! But before your code can be merged, you'll need to have signed the Individual Contributor License Agreement. Don't worry, it only takes a minute and you'll definitely get to keep your firstborn, probably. If you've already signed it for contributing to Chromium or Chromium OS, you're already done.

If you don't know what to do with your time as an official Contributor, here's some suggestions:

Really like a certain desktop environment? Fork crouton, add the target, and create a pull request.

Is your distro underrepresented? Want to contribute to the elusive and mythical beast known as "croagh"? Fork crouton, add the distro, and create a pull request.

Discovered a bug lurking within the scripts, or a papercut that bothers you just enough to make you want to actually do something about it? You guessed it: fork crouton, fix everything, and create a pull request.

Are most bugs too high-level for you to defeat? Grind up some EXP by using your fork to eat pie.

Are there other, non-Contributory ways I can help?

Yes!

But how?

There's a way For Everyone to help!

Something broken? File a bug! Bonus points if you try to fix it. It helps if you provide the output of croutonversion (or the output of cat /etc/lsb-release from Crosh) when you submit the bug.

Want to try and break something? Look through requests for testing and then do your best to brutally rip the author's work to shreds.

Look through open issues and see if there's a topic or application you happen to have experience with. And then, preferably, share that experience with others.

Find issues that need wiki entries and add the relevant info to the wiki. Or just add things to/improve things in the wiki in general, but do try to keep it relevant and organized.

Really like a certain desktop environment, but not up for coding? Open or comment on a bug with steps to get things working well.